app-delivery expects yaml output, but cdk synth only outputs json

[brucejcooper]

I'd like to report a simple bug in the app-delivery module. I'm trying to use the app-deploy module to build and self-deploy a CDK app, just like in the documentation. The problem is that the app-deploy model expects the built CFN to be in yaml format (see https://github.com/aws/aws-cdk/blob/master/packages/%40aws-cdk/app-delivery/lib/pipeline-deploy-stack-action.ts#L123), but running node_modules/.bin/cdk synth -o dist will only produce json output, no matter what options you supply.

The only way I've been able work around the problem is to do a dodgey content redirect in the buildspec.yml file

  # When redirecting, the directory must exist before the command is run.
  # TODO remove when cdk bug is resolved.
  - mkdir -p dist

  # There is a bug in CDK whereby the cdk command generates json when using the 
  # -o option, but the app-deploy target expects yaml.  To work around this, we
  # do silly buggers with redirection of the stdout, which is yaml.
  - node_modules/.bin/cdk synth -o dist > dist/CodepipelineMetaStack.template.yaml

Whilst this makes it work, it isn't very elegant and its prone to output changes in the cdk executable. Its trivial to fix, so I thought I'd raise this issue.

This is related to #2965 in that fixing that one would allow me to create a yaml file as part of a call to cdk synth. You could either fix that bug, or change the linked file to expect json instead...

[eladb]

Since JSON is YAML I am wondering what kind of error you have observed.

[caseyhoward]

The problem isn't with the contents of the file, it's with the name of the file. The error I see is "File [blah.template.yaml] does not exist in artifact [Artifact_Blah_Something]". It's looking for a file with the yaml extension but synth outputs a json extension. I'm really curious how this ever worked since it's hardcoded to look for yaml in the source code. Did "cdk synth" used to emit yaml?

[brucejcooper]

Since JSON is YAML I am wondering what kind of error you have observed.

As casey suggests, its a file naming problem.

if you look at https://github.com/aws/aws-cdk/blob/master/packages/%40aws-cdk/app-delivery/lib/pipeline-deploy-stack-action.ts#L123, you'll see that the replace changeset action is expecting a file that ends in .yaml. When the pipeline is built using the suggested command of node_modules/.bin/cdk synth -o dist the file that is created is dist/{nameofstack}.template.json. This causes the action to fail. Simply changing the expected filename to .json will fix this.

[eladb]

Got it. Confirming this is a bug in the app-delivery library.

[eklinkhammer]

As a short term fix, I added this to my buildspec:
- find dist/ -name '*.template.json' -exec rename 's/\.json$/.yaml/' \{} \;